NGC reported that the coin was a product of the conversion to steam presses at the U.S. Mint in Philadelphia.

It was described this way:

In 1836 the U.S. Mint introduced a steam-powered press to strike coins, all of which had been manufactured by hand using a screw press until that point. To coincide with this new technology, Mint engraver Christian Gobrecht modified the Capped Bust half dollar to feature a slightly revised design. Most notably, the new design had a reeded edge that replaced the lettered edge used on earlier half dollars.

These reeded edge half dollars were struck only from 1836 to 1839 and have grown in popularity with collectors in recent years. Much of this increased interest is the result of the publication of researcher Dick Graham’s “A Registry of Die Varieties of Reeded Edge Half Dollars 1836-1839,” in which he cataloged the different dies used to strike these coins.

Reeded edge half dollar die varieties are attributed by GR number, a combination of the first initials of the last names of Graham and Jules Reiver, who had written an attribution guide for these coins in 1988. The discovery coin for the GR-26 variety is a previously unknown pairing of the obverse used to strike GR-23 and the reverse used to strike GR-25.

“The 1837 GR-26 die variety is the first new die marriage discovered since publication of his book, bringing the variety count to 57 for the short series,” he explained.

NGC Research Director David W. Lange added, “This coin was submitted to NGC under our VarietyPlus® attribution service. After careful study and consultation with several top experts, we confirmed that this was indeed the discovery coin for the GR-26 variety.”